1. Field of the Invention
The present invention relates to a recording liquid for recording on an object, a liquid cartridge which contains the recording liquid, a liquid ejection cartridge which ejects the recording liquid onto the object, a liquid ejection apparatus, and a liquid ejection method.
2. Description of the Related Art
One example of a liquid ejection apparatus is an ink-jet printer which ejects ink from an ink ejection head onto an object, such as recording paper, coated paper, a plastic film, or woven fabric, in order to record images and characters on the object. The ink-jet printer has the advantages of low running cost, reduction in size of the apparatus, and ease of printing color images.
In an ink-jet printer, inks are supplied from ink cartridges which are filled with inks having a plurality of colors, such as yellow, magenta, cyan, and black, to ink liquid chambers, etc., of an ink ejection head. In the printer, a pressure is applied to the ink supplied to each ink liquid chamber, etc., by a pressure-generating element, such as a heating resistor or a piezoelectric element, disposed in the ink liquid chamber, so that the ink is ejected in the form of droplets from microscopic ink ejection ports, i.e., nozzles, provided on the ink ejection head, and the ejected ink droplets are allowed to land on an object, such as recording paper, thus printing images and characters.
The ink used for the ink-jet printer is, for example, prepared by dissolving or dispersing any of various types of dyes or pigments in a solvent. Among the various properties required for the ink, examples of important ink properties include nozzle anti-clogging properties, anti-bleeding properties to prevent ink from bleeding on the object, quick-drying properties, and long-term stability, i.e., no change in the ink's properties even if the ink is kept for a long period of time. Many studies have been conducted regarding these properties.
In addition to the important properties described above, it is also important to maintain stable ejection properties for a long period of time. As a method to meet this requirement, Japanese Unexamined Patent Application Publication Nos. 56-5871 and 57-102971 each describe the addition of a surfactant, an oxygen absorbent, or the like.
However, in ink-jet printers, if ink containing a surfactant or the like is ejected at high speed, namely, ink is ejected from one nozzle 5,000 times or more per second, for example, by driving a pressure-generating element with a pulsed current at a frequency of 5 kHz or more, movement of the ink in the ink ejection head becomes noticeable and in some cases, microscopic air bubbles or the like may be produced, resulting in problems in ink ejection. Furthermore, microscopic air bubbles may clog the nozzles, resulting in non-ejection of ink or degradation in the frequency responsiveness, such as difficulty in ejecting ink at a predetermined interval. Such degradation in ejection stability becomes noticeable as the drive frequency for driving the pressure-generating element increases, for example, to 6 kHz or 8 kHz.
In ink-jet printers, recently, the nozzle diameter has been miniaturized to a size of 20 μm or less, and the volume of one droplet has been reduced to 10 pl or less. In such a printer, when the nozzle diameter is miniaturized, the influence of microscopic air bubbles generated in the ink becomes further noticeable by causing a degradation in ejection stability. Namely, since the nozzle diameter is miniaturized, even if air bubbles are microscopic, the air bubbles may clog the nozzles, resulting in non-ejection of ink.